Aperiodic electronic blocking valve



June 3, 1952 Filed Jan. 24, 1948 INVENTORS HARRY HUBER LOTHAR BRUCK BY+C0.

AGENT-S Patented June 3, 1952 APERIODIC ELECTRONIC BLOCKING VALVE HarryHuber and Lothar kriick, Paris, France,

assignors to Compagnie Generale de Telegraphic Sans Fil, a corporationof France Application January 24, 1948, Serial No. 4,138 In FranceJanuary 29, 1947 3 Claims. (01. 315-39 1. The present invention relatesto an aperiodic blocking tube and is concerned with tubes of the typeused in radar apparatus when the transmitter and the receiver areconnected to the same aerial. mit-receive-switch or T. R. S. tubes.)

For a fixed wavelength, such tubes operate with a circuit having a highquality factor but for a fairly broad range of wavelengths it isnecessary to use aperiodic blocking tubes. In this case it is customaryto use blocking tubes without any electrodes (so-called Nullodes), whichare placed inside a coaxial transmission line. But, as is well known,the size of these tubes becomes so small when they are used forcentimetre-wave work that it is difficult to obtain a discharge which isreliably accurate either in respect of its position or as regards thecontrol of its intensity. The thickness of the glass wall becomesproportionately too great as compared with the space occupied by thedischarge, so that when the tube strikes the characteristics of the lineare not sufficiently modified.

The blocking tube which is the subject of the present invention affordsa better solution of the difiiculties referred to. One practicalembodiment of the said invention is shown (by way of example only) inthe accompanying drawing, which shows the tube in section. The blockingtube B adapted to operate on centimetre wavelengths, is interposedbetween the transmitter and the receiver in the path of a concentric orcoaxial transmission line indicated by references L and L. The walls orenvelope D of the tube are united with the outer surfaces of the saidline, the outer surfaces being designated by E and E" on the drawing,the inner conductors by I and I'. The parts J, J' are airtightinsulating joint-pieces, adapted to seal off the blocking tube and atthe respective levels of these joint-pieces a sudden change occurs inthe diameter of the internal conductor of the concentric line. Theamount of this change of diameter is such that, although there is achange of medium, there is no discontinuity in the value of thecharacteristic impedance of the line. Similarly, and according to theinvention, in a definite zone, at the centre of the tube, the diametersof the outer and inner conductors of the line both taper simultaneouslyat R and R, without there being any variation of the said impedance. Atthe place where this variation of diameters occurs, the electric fieldis of greater intensity than elsewhere; that is why this particularplace is favourable for the discharge.

(These tubes ar known as trans-' 'Furthermora'in order to obtain acertain and definite discharge at this point, it is advantageous toprovide for a suitable degree of preionization in the vicinity thereof.This can be obtained by means of an auxiliary discharge in the actualatmosphere used for the principal discharge of the tube. Such auxiliarydischarge takes place between a ring A, which is supplied by the lead H,and the outer conductor E, E (E and E are connected electrically by theconstricted part which, at the point of constriction, is provided withradially distributed perforations designated T on the drawing whichallow the ionization electrons to pass). Brackets K, K mounted uponinsulating members C, C' aiford means for mechanically supporting thedischarge system.

It is possible to provide other means of preionization. One of suchmeans consists in irradiating the discharge space, by means of aluminous lamp of toroidal shape, such lamp having its own mercury vapourdischarge and occupying the place of the ring A mentioned hereinbefore.This system has the advantage that when it is used the life of the tubeis longer.

I Furthermore, the inner wall of the outer conductor of the line,adjacent the constriction which promotes the discharge, may be coatedwith a light sensitive layer, so as to use the photo-electrons by theaction of the external mercury vapour lamp. Alternatively, this sameportion of wall may be coated with a radio-active layer, and in thatcase no other auxiliary exciting source is required.

Of course, the manufacture of the tube is so arranged that its parts canreadily be assembled for example, by interfitting the various'simpleelements.

In contradistinction to the T. R. S. tube, provided with a resonantcavity of high quality factor, there is no voltage transformation in thetube according to this invention (just as in the socalled Nullodetubes). In many cases, however, this is a small disadvantage whencompared with the advantage of being able to use wide frequency rangeswith the possibility of having a variable wavelength. There is no signalreflection, owing to the constancy of the characteristic impedance. Ifdesired, the coupling between the tube and the outer line may be suchthat it does not alter the value of the characteristic impedance.

We claim:

1. In a coaxial transmission line comprising an interio and an exteriorconductor for ultra.

7 and insi'desaid portionof the line, a'zone where said interior andexterior conductors taper s imultaneously to constitute two truncatedcones united at their tops by a cyl ndricalpo tipg 2. A device accordingto claim 41 in which means are provided on theziiiterior oi said en:velope for producing a pfei'oiiisati oniinl in; terior of said envelopein the vicinity of thesaid zone defined by the simultaneous? taper ofthe exterior and interior conductors of said linfsaid means surroundingthe reduced portion of the exterior conductor of the said line.

4.. 9m? wa d n to claim 1 c ei on the interior of said tube, a ringsurrounding the exterior conductor of said line, in the tapered portion,and means disposed on the exterior of said envelope for impressing fromoutside of said envelope onto said ring a voltage sufiicient to producea preionisation in the zone defined by. thesimultaneous reduction of thetwo line conductors.

HARRY HUBER.

LOIHAR BRiicK.

BatnR NoEs CITED Theiollowing references are of record in the file -ofthis patent;

UNITED STATES PATENTS Number Name Date 2,403,302 Richmond July 2, 19462,422,190 Fiske June 1'7, 1947

